1. Field of the Invention
The invention relates to the field of image processing, and more particularly to motion estimation used in image transmission chains with a view, in particular, to reducing the information throughput, and aims at a method and the corresponding device for estimating and hierarchically coding the motion of sequences of images.
2. Discussion of the Background
Motion estimation information is increasingly used in all parts of a high-definition television transmission chain:
at the stage for producing the images; PA1 at the stage for transmitting the images; PA1 and at the stage for receiving these same images. PA1 the first is that the complexity and therefore the performance of the motion estimating system may be higher at the production studio than they could be in an item of receiving equipment; thus, a powerful and solid motion estimator may be constructed; PA1 the second is that, at the production studio, all the information from the sequence of images to be coded is available and that the motion estimation is therefore more powerful; PA1 moreover, a motion estimation performed at the receiving end would be perturbed by transmission noise. PA1 at a first level, in partitioning the current image into 2.sup.p+1 .times.2.sup.p+1 pixel macroblocks and in determining a first field of motion vectors, which is associated with this partition into macroblocks, by using an iterative and recursive estimation algorithm initialized by motion vectors estimated for the preceding image, PA1 then, at a second level, in partitioning into quadrants each of the macroblocks and in determining, for the blocks which result therefrom, a second motion vector field by using the same estimation algorithm but initialized by vectors from the field of motion which was estimated at the preceding level, PA1 then at an ith level, i=3 to p, in partitioning each of the blocks considered at the i-1 level into quadrants and in determining, for the blocks which result therefrom, an ith motion vector field by using the same estimation algorithm initialized by vectors from the field of motion which were estimated at the preceding level, the blocks of minimum size being 2.sup.l+1 .multidot.2.sup.l+1 pixel blocks, PA1 and in determining a final motion vector field from the p resulting motion vector fields by choosing the lowest level of partition for which the motion vector associated with the corresponding block leads to the minimization of a criterion reflecting the differences of brightness between blocks communicating in the successive images via the estimated displacement vectors.
Thus, motion estimation becomes an important function in the, in particular high-definition, image transmission chain.
Currently, each item of equipment in the transmission chain has its own motion estimator. It therefore seems of great interest to provide a single motion estimator, in the production studio, which is able to feed each item of equipment in the high-definition television chain. But, as each item of equipment does not require the same characteristics for the motion information, the single motion estimator must have several possible outputs, or be parametrizable.